Techniques for transmitting packet data at a high rate in uplink are under consideration. In such packet data transmission techniques, it is necessary to allocate which communication terminal apparatus performs transmission. This allocation, namely, scheduling is determined at a base station based on information about the transmission power of a channel transmitted by a communication terminal or how much transmission power can be used for transmitting packet data, the amount of transmission data to be transmitted by the communication terminal apparatus, and the like. Scheduling information determined at the base station is transmitted to each communication terminal apparatus in communication, and the communication terminal apparatus transmits packet data to the base station based on the received scheduling result information. In DPCHs (Dedicated Physical Channels) which are used in a WCDMA system and dedicated channels for carrying out transmission power control, there are a DPDCH (Dedicated Physical Data Channel) which is actual transmission data such as a packet and a DPCCH (Dedicated Physical Control Channel) which is made up of a pilot signal and the like. In high-rate uplink packet transmission, in order to enable the base station to perform scheduling, the communication terminal apparatus measures the transmission power of the DPCCH having the pilot signal for performing closed loop transmission power control and reports information of the measured DPCCH transmission power to the base station. By receiving the transmission power information from the communication terminal apparatus, the base station can know whether the communication terminal apparatus is located at an edge of a cell and in a state of not having a margin for transmission power, or is located near the base station and performs transmission at a high rate.
FIG. 1 shows a DPCCH frame format which is defined in 3GPP TS25.211. In the DPCCH, one frame has a length of 10 msec. and is made up of 15 slots of slots #0 to #14. Each slot is made up of pilot symbol #51, TFCI (Transport Format Combination Indicator) #52, FBI (Feedback Indicator) #53 and TPC (Transmit Power Control) #54.
When a FDD (Frequency Division Duplex) scheme is used like WCDMA that is a worldwide standard for mobile communication, each base station can use a plurality of carriers within allocated frequency band. In this case, it is necessary for a communication terminal apparatus to seek for the plurality of carriers used by the same base station. For example, if the communication terminal apparatus has only one oscillator, when the communication terminal apparatus seeks for a carrier of 2,050 MHz in downlink, a carrier frequency difference between uplink and downlink is 190 MHz in the FDD, and therefore transmission at 1,950 MHz in uplink is impossible. In such a case, the communication terminal apparatus uses a compressed mode having a temporary transmission stop period called a gap in uplink in order to transmit data that cannot be transmitted. In a frame of the compressed mode, the transmission power is temporarily increased to prevent quality deterioration by a gain decrease due to transmission stop during the gap. For ease of explanation, FIG. 2 shows a drawing assuming a case where power does not change due to closed loop transmission power control. When transmission data is made up of normal frames #60 and #62 which are not in the compressed mode and frame #61 in the compressed mode having gap #63, the transmission power of each slot of frame #61 in the compressed mode is set higher by ΔP64 than the transmission power of each slot of the normal frames which are not in the compressed mode.
A technique to achieve a high rate and low delay in uplink, which is called uplink enhancement, is under consideration (for example, Non-patent Document 1). In the uplink enhancement, it is proposed that, in order to increase channel estimation accuracy in a case of transmitting high-rate data, pilot transmission power should be increased temporarily. That is, as shown in FIG. 3, in the case of performing transmission at a high transmission rate in a DPCCH including pilot symbol #71, TFCI #72, FBI #73 and TPC #74, the transmission power of pilot symbol #71 is set higher by ΔP75 than the case of performing transmission at a normal transmission rate.
Non-patent Document 1: 3GPP, R1-040497, Boosting of DPCCH pilot power for E-DCH, Samsung